Patients with low-risk disease (WBC no greater than 10,000/mm3, age 3 to 6 years, no prominent lymphadenopathy (less than 3 cm in diameter in each nodal region), normal CSF, no mediastinal mass, no enlargement of liver or spleen, and no cranial nerve palsies) proceed directly to maintenance therapy. All other patients are considered high risk, and they repeat first induction therapy and then proceed to consolidation therapy.